A boost pressure control system for an internal combustion engine is described in Patent Document 1. According to this boost pressure control system, in the case where a boost pressure needs to be raised to be made coincident with a target boost pressure as a target value thereof, the boost pressure is controlled through open-loop control while a difference between the boost pressure and the target boost pressure (this difference will be referred to hereinafter as “a boost pressure deviation”) is equal to or larger than a predetermined value, and the boost pressure is controlled through feedback control if the boost pressure deviation becomes smaller than the predetermined value. It should be noted herein that in the case where a rate of rise in the boost pressure in the control of the boost pressure through open-loop control (this control will be referred to hereinafter as “boost pressure OL control”) prior to the start of the control of the boost pressure through feedback control (this control will be referred to hereinafter as “boost pressure FB control”) is relatively large, the rate of rise in the boost pressure in boost pressure FB control is made smaller than in the case where the rate of rise in the boost pressure in boost pressure OL control prior to the start of boost pressure FB control is relatively small.
Thus, the following effects are obtained. That is, in the boost pressure control system described in Patent Document 1, while the boost pressure deviation is relatively large, the boost pressure is controlled through open-loop control. Thus, the boost pressure is raised at a relatively large rate of rise. Accordingly, this allows the boost pressure to swiftly approach the target boost pressure. Then, if the boost pressure deviation becomes relatively small, the boost pressure is controlled through feedback control. It should be noted herein that if the rate of rise in the boost pressure during boost pressure FB control is not limited at all, the possibility of the occurrence of a so-called overshoot, namely, an excess of the boost pressure far above the target boost pressure during boost pressure FB control is higher in the case where the rate of rise in the boost pressure in boost pressure OL control prior to the start of boost pressure FB control is relatively large than in the case where the rate of rise in the boost pressure in boost pressure OL control prior to the start of boost pressure FB control is relatively small. However, in the boost pressure control system described in Patent Document 1, the rate of rise in the boost pressure during boost pressure FB control is made smaller in the case where the rate of rise in the boost pressure during boost pressure OL control prior to the start of boost pressure FB control is relatively large than in the case where the rate of rise in the boost pressure during boost pressure OL control prior to the start of boost pressure FB control is relatively small. Therefore, an overshoot, namely, an excess of the boost pressure far above the target boost pressure during boost pressure FB control is restrained from occurring. That is, according to the boost pressure control system described in Patent Document 1, an effect of making it possible to make the boost pressure swiftly approach the target boost pressure and suppress an overshoot, namely, an excess of the boost pressure far above the target boost pressure is obtained.